package com.zhw.mybatis.mapper;

import com.zhw.mybatis.mapping.MappedStatement;
import com.zhw.mybatis.sqlSession.ZhwSqlSession;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;

//因为 mybatis 是根据接口来实现数据库操作的，接口是无法生成对象的，所以我们用 一个类使用动态代理的方式
//去代替 所有接口生成后的类
public class MapperProxy<T> implements InvocationHandler {
    private final ZhwSqlSession zhwSqlSession;
    private final Class<T> mapperInterface;

    public MapperProxy(ZhwSqlSession zhwSqlSession, Class<T> mapperInterface) {
        this.zhwSqlSession = zhwSqlSession;
        this.mapperInterface = mapperInterface;
    }

    //执行Mapper接口的方法
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        //mapperInterface 执行方法
        String namespace = method.getDeclaringClass().getName();
        MappedStatement mappedStatement = zhwSqlSession.getConfiguration().getMappedStatement(namespace);
        if(mappedStatement.getId().equals(method.getName())){
            String sql = parse(mappedStatement.getSql());
            Object query = zhwSqlSession.selectOne(sql, args,mappedStatement.getResultType());
            return query;
        }
        return null;
    }

    //将sql中的 #{} 代替为 ?
    public String parse(String text) {
        String openToken = "#{";
        String closeToken = "}";
        if (text == null || text.length() == 0) {
            return "";
        }
        // search open token
        int start = text.indexOf(openToken);
        if (start == -1) {
            return text;
        }
        char[] src = text.toCharArray();
        int offset = 0;
        final StringBuilder builder = new StringBuilder();
        StringBuilder expression = null;
        while (start > -1) {
            if (start > 0 && src[start - 1] == '\\') {
                // this open token is escaped. remove the backslash and continue.
                builder.append(src, offset, start - offset - 1).append(openToken);
                offset = start + openToken.length();
            } else {
                // found open token. let's search close token.
                if (expression == null) {
                    expression = new StringBuilder();
                } else {
                    expression.setLength(0);
                }
                builder.append(src, offset, start - offset);
                offset = start + openToken.length();
                int end = text.indexOf(closeToken, offset);
                while (end > -1) {
                    if (end > offset && src[end - 1] == '\\') {
                        // this close token is escaped. remove the backslash and continue.
                        expression.append(src, offset, end - offset - 1).append(closeToken);
                        offset = end + closeToken.length();
                        end = text.indexOf(closeToken, offset);
                    } else {
                        expression.append(src, offset, end - offset);
                        break;
                    }
                }
                if (end == -1) {
                    // close token was not found.
                    builder.append(src, start, src.length - start);
                    offset = src.length;
                } else {
                    builder.append("?");
                    offset = end + closeToken.length();
                }
            }
            start = text.indexOf(openToken, offset);
        }
        if (offset < src.length) {
            builder.append(src, offset, src.length - offset);
        }
        return builder.toString();
    }

}
